Methods for whitening teeth

ABSTRACT

In a tooth whitening method, a whitening composition is applied to at least one tooth. The whitening composition is maintained on the at least one tooth for a first time period. After the first time period, a light radiation is directed toward the at least one tooth for a second time period. The first time period has a duration greater than 50% of a total duration of the first and second time periods. The whitening composition is removed from the at least one tooth.

CROSS REFERENCE TO RELATED APPLICATION

This application claims priority to provisional U.S. App. No. 61/354,926filed Jun. 15, 2010, the substance of which is incorporated herein byreference.

FIELD

This application relates to tooth whitening compositions, products,devices, and methods.

BACKGROUND

Many approaches are used to whiten teeth. One common approach usesabrasives (for example, in toothpastes and prophyaxis pastes) incombination with a polishing action to polish discolorations and stainsoff of the surface of the teeth. Because abrasives only work on thesurface of the teeth, the intrinsic color of the teeth is largelyunchanged. As such, abrasives only offer limited effectiveness inwhitening of the teeth.

Another approach is the use of chemical whitening actives in acomposition to intrinsically and extrinsically whiten teeth. A chemicalwhitening active is applied to the teeth for a period of time to allowthe active to act upon the teeth and provide an improvement in thewhiteness of the teeth. Whiteners are commonly applied to the teethusing toothpastes, rinses, gums, floss, tablets, strips and trays. Acommon chemical whitening active is peroxide. Often, strips and traysare used to apply peroxide for contact times beyond that achievable withtypical toothbrushing. Concentration of the whitening active, contacttime and number of applications are some of the primary parameters whichdictate the rate and amount of whitening achieved with peroxide basedtooth whitening compositions. Whitening products using a strip ofmaterial in combination with a chemical whitening active are described,for example, in U.S. Pat. Nos. 5,891,453 and 5,879,691, the disclosuresof which are incorporated herein by reference. The whitening compositiondescribed therein can include a peroxide active.

Efforts to increase the whitening efficacy of products in order todeliver a more satisfying product experience have included increasingthe concentration of peroxide for a faster whitening per time of use.Maintaining the peroxide on the tooth surface for longer contact timesand/or for an increased number or frequency of applications have alsobeen employed for increased whitening. While increasing concentration,increasing wear time and increasing number of applications can beeffective methods of achieving higher degrees of tooth whitening from atooth whitening product, each of these parameters also may have anegative impact on the consumer's experience.

Increasing the concentration of the peroxide in the whiteningcomposition, holding all other parameters essentially constant, canproduce more tooth sensitivity and cause more soft tissue irritation.Sufficiently high concentrations of peroxide may require a physicalbarrier, such as a rubber dam, to prevent the peroxide from contactingand burning the soft tissue thereby making the use of the high peroxideconcentrations inconvenient and impractical for unsupervised at home andrepeated use. In fact, even conventional in-office tooth whiteningcompositions having a peroxide concentration equivalent to as low as 13%hydrogen peroxide, often utilize a rubber dam to protect the soft tissueduring the bleaching process. Increasing the use time and/or frequencygenerally increases the amount of tooth sensitivity and gingivalirritation as well as make the product more inconvenient to use.

SUMMARY

The present application describes a method for whitening teeth usinglight radiation to photochemically activate a tooth stain for enhancedwhitening by a bleaching or oxidizing agent.

Accordingly, in an exemplary tooth whitening method of the presentapplication, a whitening composition is applied to at least one tooth.The whitening composition is maintained on the at least one tooth for afirst time period. After the first time period, a light radiation isdirected toward the at least one tooth for a second time period. Thefirst time period has a duration greater than about 50% of a totalduration of the first and second time periods. The whitening compositionis removed from the at least one tooth before, during, or after thesecond time period.

In accordance with another aspect of the present application, anexemplary light enhanced tooth whitening kit includes a strip sized tocover one or more teeth, with the strip including a layer of a toothwhitening composition. The kit further includes a portable light sourceconfigured to emit light radiation having an intensity of no greaterthan about 150 mW/cm².

BRIEF DESCRIPTION OF THE DRAWINGS

Further features and advantages of the invention will become apparentfrom the following detailed description made with reference to theaccompanying drawings, wherein:

FIG. 1 illustrates a light enhanced tooth whitening kit;

FIG. 2 is a cross-sectional plan view of human dentition, illustratingapplication of the light enhanced tooth whitening kit of FIG. 1 fortreatment of a front surface of a plurality of teeth;

FIG. 3 is a cross-sectional side elevation view of a tooth of FIG. 2,taken along line 3-3 thereof;

FIG. 4 is a schematic illustration of the 1976 CIE LAB color space;

FIG. 5 is a graph illustrating the interplay between whitening efficacy,soft tissue tolerability, peroxide concentration, composition loadingand peroxide dosing, according to a non-light enhanced tooth whiteningmethod;

FIG. 6 is a graph illustrating the interplay between duration of lightradiation treatment and tooth whitening efficacy; and

FIG. 7 is a graph illustrating the interplay between intensity of lightradiation treatment and tooth whitening efficacy.

DETAILED DESCRIPTION

This Detailed Description merely describes embodiments of the inventionand is not intended to limit the scope of the claims in any way. Indeed,the invention as claimed is broader than and unlimited by the preferredembodiments, and the terms used in the claims have their full ordinarymeaning.

Also, while the exemplary embodiments described in the specification andillustrated in the drawings relate to methods of whitening teethinvolving treatment with a tooth whitening composition including aperoxide active, it should be understood that many of the inventiveaspects described herein may be applied to other tooth whiteningmethods, including for example methods involving the use of other toothwhitening compositions.

As used herein the phrase “whitening efficacy” is intended to refer tothe amount of change in tooth color. The color change can be measuredaccording to the LAB color scale. FIG. 4 illustrates a model of the 1976CIE LAB color space. The luminance or lightness (L*) value measuresbrightness and varies from a value of one hundred for perfect white tozero for black assuming a* and b* are zero. The a* value is a measure ofredness when positive, gray when zero and greenness when negative. Theb* value is a measure of yellowness when positive, gray when zero andblueness when negative. Generally, teeth appear whiter as: the L valueincreases meaning they become brighter, the a* value increases ordecreases depending upon whether the stained teeth have a green or redtint prior to whitening, and the b* value decreases meaning they becomeless yellow. While this is the general relationship for perceivedwhitening, the b* value might also slightly increase if the magnitude ofthe increase of the L* value is large enough. Similarly, the L* valuemight also decrease if the magnitude of the decrease of the b* value islarge enough to overshadow the less significant change in L*. Becausethe color of actual stained teeth varies by different geographies,whether the a* value increases or decreases for whitening can begeography dependent. For instance, stained teeth have a brown or redtint in the United States while stained teeth have a green tint inChina.

A method of measuring tooth color change in-vivo has been described inU.S. Pat. No. 6,949,240 and ASTM E2466-06, the entire disclosures ofwhich have been incorporated herein by reference. In such a method, adigital camera is used to compare baseline and post-whitening toothcolor to RGB color standards imaged to establish calibration set-points.The RGB values are transformed into L*a*b* values after calibrationusing transformation equations, and the resulting data is used tocalculate product whitening performance in terms of changes in L*(luminance), a* (red-green balance), and b* (yellow-blue balance). Anoverall color change is calculated using the equationΔE=(ΔL*²+Δa*²+Δb*²)^(1/2).

When ΔL* is positive, Δb* is negative and a* is moving towards zero, ΔErepresents an improvement in tooth whiteness. AE is a scalar value, andtherefore it represents the magnitude of the color change, but not thedirection. For that reason, the direction of the changes in theindividual color components L*, a* and b* must be evaluated to determinewhether the ΔE value represents an improvement in tooth whiteness.

Light radiation has been employed in tooth whitening procedures incombination with the application of an oxidizing agent to the teeth.However, the previous use of light radiation in tooth whiteningprocedures, while increasing tooth whitening efficacy, may produceincreased tooth and soft tissue sensitivity and discomfort, or otherharmful effects. As one example, U.S. Pat. No. 4,661,070 describes amethod in which a concentrated solution of hydrogen peroxide is appliedto the teeth, which are then exposed to infrared and ultraviolet light.The infrared light radiation is intended to produce heat to penetratethe outer tooth surface and heat activate the peroxide, while theultraviolet light is intended to provide direct bleaching of the toothstains. However, excessive temperature increases in the pulpal tissuemay damage teeth and cause sensitivity and discomfort. Further, healthhazards associated with exposure to ultraviolet light are also aconcern.

Tooth whitening using photoactivation of a radiant energy absorbingsubstance or photosensitizing agent (for example,1-hydroxyethylidene-1,1-diphosphonic acid) applied to a dental patient'steeth has been described for example in U.S. Pat. Nos. 5,785,527,6,162,055, and 6,416,319, the entire disclosures of which areincorporated herein by reference. In such examples, the photosensitizingagent may be applied prior to or in combination with an oxidizing agent(for example, hydrogen peroxide), such that light radiation applied tothe treated teeth is absorbed by the photosensitizing agent, which inturn activates the oxidizing compound to whiten the teeth. However,inadvertent exposure of a user's soft tissue to the photosensitizingagent may result in irritation and increased sensitivity uponapplication of the light radiation.

Clinical testing of light radiation enhancement of in-office, highconcentration peroxide gel tooth whitening treatments has identifiedmeasurable increases in whitening efficacy, as compared to peroxide geltooth whitening treatments alone. See Gerald Kugel et al., ClinicalTrial Assessing Light Enhancement of In-office Tooth Whitening, JOURNALOF ESTHETIC AND RESTORATIVE DENTISTRY, Oct. 1, 2009, pp. 336-346, theentire disclosure of which is incorporated herein by reference. However,these increases in tooth whitening efficacy were accompanied bysignificant increases in tooth sensitivity. In the clinical test, six ofthe eleven test subjects treated with peroxide gel and light radiationreported moderate to severe tooth pain, with three of the test subjectsdiscontinuing treatment due to severe tooth pain. By comparison, onlythree of the eleven test subjects treated with peroxide gel withoutlight radiation reported moderate pain, with none of these test subjectsexperiencing severe pain. It is not known whether a photosensitizingagent was included in the peroxide gel that was used, nor is it knownwhether such use of a photosensitizing agent in the peroxide gel,combined with the prolonged light treatment, may have contributed to thesignificant increase in tooth sensitivity.

In other examples, a light radiation may be selected to activate thetooth stains directly, without the use of a photosensitizing agent, toenhance bleaching by an oxidizing compound. Light having a wavelengthselected to correspond with a tooth chromogen (or stain) moleculeabsorption wavelength may be applied to the teeth to activate the stainmolecules for oxidation by the oxidizing compound. In such an example,the light radiation may not activate or affect the oxidizing compound.The oxidizing compound may be provided as a transparent or translucentmaterial to allow the light radiation to reach the treated teeth.Absorption of the light radiation by the stain “activates” the stain bypromoting electron activity or reactivity, such that a bleaching agentapplied to the stain more effectively oxidizes the stain, therebyremoving a greater portion of the stain, as compared to oxidation by ableaching agent of a stain that has not been activated by this lightradiation.

Even without a photosensitizing agent, exposure of the gums and othersoft tissue to the light radiation may cause some activation of thistissue. This may result in increased sensitivity and irritation when thesame tissue is exposed to higher concentrations of peroxide or someother oxidizing agent.

According to an inventive aspect of the present application, applicationof light radiation to teeth treated with a tooth whitening compositionhaving an oxidizing agent may be limited to a delayed or final portionof the total duration of exposure of the teeth to the tooth whiteningcomposition. By limiting the light radiation to just a portion of theentire duration of the treatment, irritation and sensitivity of theteeth and soft tissue exposed to the oxidizing agent may be reduced.Additionally, temperature increases within the user's mouth may also bereduced. Further, by limiting light radiation to a final portion of theentire duration of treatment, the application of light is providedduring a period at which absorption of the oxidizing agent into theteeth is maximized, and dissipation of the oxidizing agent away from thesoft tissue (for example, by dissolution into the user's saliva) hasoccurred. As still another benefit, the application of light radiationfor a reduced period of time reduces the duration of an open mouth orretracted lip condition, thereby reducing the soreness and oraldehydration associated with these conditions.

Accordingly, a predetermined duration of tooth whitening treatment isdivided into two time periods: a delay or first time period and a lightradiation or second time period. During the delay period, a chemicalwhitening composition is maintained on a user's teeth without theapplication of light radiation. During a subsequent second time period(the light radiation period), light radiation is applied to the teeth.The light radiation may be applied through a translucent chemicalwhitening composition (and any corresponding translucent carrier for thecomposition, such as a tray or adhesive strip). In another embodiment,the tooth whitening composition (and any corresponding carrier) may beremoved from the teeth after the delay period and before the lightradiation period, as described in greater detail below, or during thelight radiation period. In one embodiment, the delay period is greaterthan the light radiation period, or greater than 50% of a total durationof the delay and light radiation periods, such that the teeth areexposed to light radiation for less than half of the entire duration ofthe tooth whitening treatment. The delay period may also be greater thanabout 60%, greater than about 70%, greater than about 80%, greater thanabout 90%, greater than about 95%, or greater than about 96%, or greaterthan about 97%, or greater than about 98%, or greater than about 99%, orgreater than about 99.5%, or greater than about 99.9%, or between about80% and about 90% of the total duration of the delay and light radiationperiods.

The delay period, light radiation period, and total duration of thedelay and light radiation periods may be selected from a variety ofsuitable numbers and ranges. For example, the delay period may rangefrom about 2 minutes to about 480 minutes, or from about 5 minutes toabout 55 minutes, or from about 15 minutes to about 25 minutes. Inanother embodiment, the delay period may be at least 1, 2, 5, 7, 10, 15,20, 25, 30, 40, 50, or 60 minutes, but less than 480, 120, 90, 60, 50,40, 30, 25, 20, 15, 10, 5, or 2 minutes.

The light radiation period may range for example from about 3 seconds toabout 30 minutes, or from about 30 seconds to about 10 minutes, or fromabout 2 minutes to about 5 minutes. In another embodiment, the lightradiation period may be at least 1, 2, 5, 7, 10, 15, 20, 25, 30, 40, 50,or 60 seconds, 2, 3, 4, minutes but less than 5, 4, 3, 2, or 1 minutes,50, 40, 30, 25, 20, 15, 10, or 5 seconds.

The total duration of the delay and light radiation periods may rangefor example from about 4 minutes to about 500 minutes, or from about 10minutes to about 60 minutes, or from about 15 minutes to about 30minutes. In another embodiment, the total duration may be at least 4, 5,7, 10, 15, 20, 25, 30, 40, 50, 60, 90, 120, 180, or 240 minutes, butless than 500, 480, 420, 360, 300, 240, 80, 120, 90, 60, 50, 40, 30, 20,or 15 minutes. In some applications, a tooth whitening composition andcarrier may be designed for overnight use, such that a relatively longdelay period (for example, between about 360 minutes and about 480minutes) occurs while the user is sleeping.

Thus, in varying embodiments, the total duration may be at least 4, 5,7, 10, 15, 20, 25, 30, 40, 50, 60, 90, 120, 180, or 240 minutes, butless than 500, 480, 420, 360, 300, 240, 80, 120, 90, 60, 50, 40, 30, 20,or 15 minutes; combined with a light radiation period of at least 1, 2,5, 7, 10, 15, 20, 25, 30, 40, 50, or 60 seconds, 2, 3, 4, minutes butless than 5, 4, 3, 2, or 1 minutes, 50, 40, 30, 25, 20, 15, 10, or 5seconds; further combined with a delay period of at least 1, 2, 5, 7,10, 15, 20, 25, 30, 40, 50, or 60 minutes, but less than 480, 120, 90,60, 50, 40, 30, 25, 20, 15, 10, 5, or 2 minutes.

Additionally, the tooth whitening process may include a third timeperiod or second delay period after the light radiation period, duringwhich the tooth whitening composition remains on the teeth without lighttreatment prior to removal. This second delay period may range forexample from about 1 minute to about 30 minutes.

In one exemplary tooth whitening method, an approximately thirty minutetooth whitening treatment includes an approximately twenty-five minutedelay period and an approximately five minute light radiation period. Inanother exemplary tooth whitening method, an approximately thirty minutetooth whitening treatment includes an approximately twenty-nine andone-half minute delay period and a light radiation period ofapproximately 30 seconds.

Other exemplary tooth whitening regimens are listed in Table 1 below:

TABLE 1 Exemplary Delay and Light Radiation Periods for Tooth WhiteningTreatments Delay Period Light Period Total % Delay (mins) (mins) (mins)Period 2 2 4 50.00 4 2 6 66.67 10 3 13 76.92 10 0.5 10.5 95.24 15 3 1883.33 15 0.5 15.5 96.77 15 5 20 75.00 20 0.5 20.5 97.56 20 1 21 95.24 203 23 86.96 20 5 25 80.00 25 0.05 25.05 99.80 25 0.5 25.5 98.04 25 1 2696.15 25 3 28 89.29 25 5 30 83.33 25 10 35 71.43 30 0.05 30.05 99.83 300.5 30.5 98.36 30 1 31 96.77 30 3 33 90.91 30 5 35 85.71 30 10 40 75.0060 0.05 60.05 99.92 60 0.5 60.5 99.17 60 5 65 92.31 120 0.5 120.5 99.59120 5 125 96.00 120 10 130 92.31 120 60 180 66.67 360 0.5 360.5 99.86360 5 365 98.63 360 10 370 97.30 480 0.5 480.5 99.90 480 5 485 98.97 48010 490 97.96 480 20 500 96.00

The durations of the delay and light radiation periods of the toothwhitening treatment may be selected based on several factors. Forexample, the delay period may be selected to allow the oxidizing orbleaching agent sufficient time to reach the tooth stains below theouter surfaces of the teeth before light activation of the stains. Inone such embodiment, a delay period sufficient for absorption of aneffective amount of peroxide into the teeth is selected for delaying theapplication of light radiation until a period of increasedeffectiveness. Because the applied light radiation activates the toothstains directly, as enhanced by the absorbed oxidizing agent, theresidual tooth whitening composition on the surface of the teeth (andany tooth whitening composition carrier) may be removed from the teethat the end of the delay period and prior to the application of lightradiation. In one such tooth whitening process, the carrier and/or thetooth whitening composition may be provided in a non-transparent,non-translucent, or opaque material, as the carrier and/or toothwhitening composition will have been removed prior to light treatment.The ability to use non-transparent, non-translucent, or opaque materialsmay increase the number of types of materials that may be used for thecarrier and tooth whitening composition. Additionally, in someapplications, the use of non-transparent, non-translucent, or opaquematerials for the tooth whitening composition or carrier may prevent theirritation or sensitivity that may otherwise result from a combinationof light radiation and excessive amounts of tooth whitening compositionon the teeth and soft tissues.

As another example, the delay period may be selected to allow bleachingagent on the soft tissue surrounding the treated teeth to dissipate orbe diluted (for example, by saliva) prior to any application of lightradiation. This may reduce any soft tissue irritation that may otherwiseresult from a combination of light radiation and bleaching agent on thesoft tissue. In one such embodiment, a time period sufficient to reducea peroxide concentration at the soft tissue to below a thresholdconcentration is selected for delaying the application of lightradiation until a period of reduced susceptibility to soft tissueirritation. For example, the selected time period may be sufficient toreduce a peroxide (or other bleaching agent) concentration to less thanabout 2% (weight for weight), less than about 1%, less than about 0.5%,less than about 0.25%, less than about 0.1%, less than about 0.05%, lessthan about 0.025%, less than about 0.0125% or less than about 0.005%.

The duration of the light radiation period of the tooth whiteningtreatment may be selected to increase whitening efficacy whileminimizing tooth and soft tissue sensitivity. Clinical testing, asdescribed in Example I below, has shown greater increases in luminance(ΔL*) and yellowness reduction (Δb*), as compared to treatment withoutlight enhancement, as the light radiation period is increased at theconclusion of treatment. One of ordinary skill in the art will recognizethat additional testing may be performed using a greater range of delayperiods and light radiation periods in conjunction with any suitabletooth whitening composition, to determine an appropriate delay period ofa total time period and an appropriate light radiation period of thetotal time period, to provide increased whitening efficacy whileminimizing tooth and soft tissue sensitivity, in accordance with thepresent application.

While a minimum light intensity may be required to activate tooth stainsfor enhanced whitening, according to an aspect of the presentapplication, variations in light intensity above a required thresholdmay have minimal impact on whitening efficacy. Clinical testing, asdescribed in Example II below, has shown that while light intensities aslow as approximately 41.5 mW/cm² (corresponding to light emitted from aLite-ON Technology Corp. LED part #LTL1CHTBK5 BIN: QBOY 470 nm suppliedwith about 10 mA of current) resulted in significant improvements inincreased luminance and reduced yellowness (as compared to treatmentwithout light enhancement), increasing light intensity to as much asapproximately 134.7 mW/cm² (corresponding to light emitted from theabove referenced Lite-ON Technology Corp. LED supplied with about 50 mAof current) resulted in only marginal improvements in whiteningefficacy. This suggests that low intensity (at least as low as about41.5 mW/cm²) light is sufficient to activate the tooth stains to anelevated quantum energy level, while the increased intensity (at leastas high as about 134.7 mW/cm²) light is insufficient to elevate thetooth stains to the next quantum energy level for greater activation.

The effectiveness of low intensity light radiation treatment mayfacilitate home use of the light enhanced tooth whitening process, asself-application of the low intensity light radiation would likely besafe for adult use. For example, low intensity light radiation is lesslikely to result in increased temperatures at the teeth or in the mouth,and is less likely to cause oral dehydration. The use of low intensitylight also reduces the risk of damage to the eyes. In-home applicationof a low-intensity light enhanced tooth whitening treatment may befurther facilitated by use of a tooth whitening composition and carrierthat provides for controlled dosing of a bleaching agent withoutrequiring isolation of the surrounding soft tissue. Examples of suitabletooth whitening products include the strip-based tooth whiteningproducts described in the incorporated U.S. Pat. No. 6,949,240.

Accordingly, a light enhanced tooth whitening kit 10 for home use may beprovided, as shown in FIGS. 1-3. The kit 10 may include a translucentstrip 14 sized to cover one or more teeth 22, with the strip including alayer 12 of a translucent tooth whitening composition disposed on asurface 28 of the strip 14. The kit 10 further includes a portable lightsource 25 (for example, a flashlight) configured to emit light radiationhaving a maximum energy output of about 10,000 millicandelas (mcd) or amaximum intensity of about 150 mW/cm², or some other maximum energyoutput or intensity that is safe for use near the eyes yet sufficient toactivate the tooth stains. The portable light source may be held againstthe tooth whitening composition carrier or directly against the teeth(for example, if the carrier has been removed prior to light radiationtreatment). The portable light source may also be held at a suitabledistance from the teeth, such as for example between about 0.5 cm andabout 3 cm or approximately 2 cm. The resulting light intensity to whichthe teeth are exposed will depend on the distance of the light sourcefrom the teeth and the energy output of the light source. Exemplaryranges of light intensity at the teeth during the light radiation periodof a light enhanced tooth whitening process include for example betweenabout 0.05 mW/cm² and about 200 mW/cm², between about 0.1 mW/cm² andabout 180 mW/cm², between about 1 mW/cm² and about 160 mW/cm², betweenabout 5 mW/cm² and about 140 mW/cm², between about 10 mW/cm² and about120 mW/cm², between about 20 mW/cm² and about 100 mW/cm², between about30 mW/cm² and about 80 mW/cm², and between about 40 mW/cm² and about 60mW/cm². In other examples, light intensity at the teeth during the lightradiation period of a light enhanced tooth whitening process may bebetween about 40 mW/cm² and about 140 mW/cm², or approximately 42mW/cm², or approximately 108 mW/cm², or approximately 135 mW/cm².

The portable light source may optionally include a timer for indicatingstarting or stopping points for the delay period and/or the lightradiation period, and may be configured to limit the emission of lightradiation to the latter period. In another embodiment, a tooth whiteningcomposition carrier may be provided with a portable light source (forexample, one or more LED chips) disposed on or in the carrier, such thatlight may be directed onto the teeth by the carrier. In one suchexample, the carrier may further include a timer circuit that delaysillumination of the portable light source for a predetermined delayperiod, and then illuminates the teeth for a predetermined lightradiation period.

The light source 25 utilized for the light enhanced tooth whiteningtreatment may be selected to provide light radiation at a wavelengththat is best absorbed by the tooth stains. The light radiation may beselected to be at a wavelength corresponding to a light colordiametrically opposite the stain color, as identified for example on the1976 CIE LAB color scale (see FIG. 4). By utilizing a diametricallyopposite light color, absorption of the light by the stain may beincreased or enhanced. For example, yellow stains (as commonly presenton teeth to be whitened) may better absorb blue light (approximately380-520 nm). As such, the light source may be selected to provide lightradiation at a wavelength of about 400 nm to about 520 nm, or about 440nm to about 490 nm, or an average wavelength of approximately 440 nm, orapproximately 450 nm, or approximately 460 nm, or approximately 470 nm,or approximately 480 nm, or approximately 490 nm. As another example,green stains may better absorb red light, such as for example lighthaving a wavelength of about 600 nm to about 780 nm. As such, a lightsource for use in whitening green stains may be selected to providelight radiation at a wavelength of about 600 nm to about 780 nm, orabout 680 nm to about 720 nm, or an average wavelength of approximately680 nm, or approximately 690 nm, or approximately 700 nm, orapproximately 710 nm, or approximately 720 nm.

Additionally or alternatively, the tooth whitening composition orcarrier (for example, a tray or strip) may be configured to shade,filter, or otherwise block undesirable light intensities andwavelengths, thereby adapting the light radiation from the light sourcethat reaches the tooth stain to be within desired ranges of intensityand wavelength. For example, a tooth whitening composition carrier maybe provided in a translucent material selected to block up to about 30%of light, or up to about 50% of light, or up to about 70% of light. Asanother example, a tooth whitening composition carrier may be providedin a translucent material selected to block light having a wavelengthgreater than about 780 nm, or greater than about 700 nm, or greater thanabout 520 nm, or less than about 300 nm, or less than about 380 nm.

Many different tooth whitening compositions and application methods maybe utilized in combination with the light radiation treatment describedabove. For example, peroxide based tooth whitening compositions withvarying concentrations of peroxide may be provided. Other additives mayalso be provided in the composition, including for examplephotosensitizing agents, gelling agents, humectants, pH adjustingagents, stabilizing agents, desensitizing agents, and acceleratingagents or bleach activators. The composition may be provided in the formof a viscous liquid, paste, gel, solution, or any other state or phasethat may be applied to the teeth. Further, the tooth whiteningcomposition may be applied directly to the teeth, or may be contained bya tray placed over the teeth or provided on a strip of flexible materialconfigured to be applied to the tooth surfaces to be whitened. Examplesof such tooth whitening compositions and application methods aredescribed in U.S. Pat. No. 6,949,240, and U.S. Application PublicationNo. 2003/0152528, the entire disclosures of which are incorporatedherein by reference.

Several factors may be considered in selecting an appropriate whiteningcomposition and application method, including for example whiteningefficacy, soft tissue tolerability, peroxide concentration, andwhitening composition loading. Generally, in non-light enhanced toothwhitening applications, as peroxide concentration increases, whiteningefficacy increases as shown by the upward slope of the efficacy curvesof the graph of FIG. 5, described in greater detail in U.S. Pat. No.6,949,240. Additionally, soft tissue tolerability decreases as peroxideconcentration increases, as shown by the downward slope of thetolerability curves of the graph of FIG. 5. From this family of curves,it will be appreciated that it is possible to maintain acceptable softtissue tolerability while increasing whitening efficacy by increasingthe peroxide concentration to relatively high levels if there is anappropriate decrease in composition loading. Stated another way, it ispossible to increase the concentration of the peroxide active to achieveimproved whitening efficacy while maintaining acceptable soft tissuetolerability, without the use of artificial barriers, by properlyselecting the composition loading. This relationship can also becharacterized by a parameter, peroxide density, which is the ratio ofthe amount of peroxide active or peroxide dose (mg) to the surface area(cm²) of the thin layer that is applied to the tooth surfaces andadjacent soft tissue of the oral cavity. This surface area may bedifferent than the “exposed surface area” and/or “unexposed surfacearea,” as discussed in U.S. Pat. No. 6,949,240.

In one embodiment of U.S. Pat. No. 6,949,240, so long as the peroxidedensity is less than about 1.3 mg peroxide/cm², there can be anacceptable tradeoff between soft tissue tolerability and whiteningefficacy for peroxide concentrations greater than at least about 7.5%.While extremely high peroxide concentrations can be surprisinglyutilized, generally it is desirable to utilize peroxide concentrationsless than 60% and, even more desirable to have a peroxide density lessthan about 1.3 mg/cm² for tooth whitening applications, because the softtissue tolerability is acceptable to very good. This controlled peroxidedensity may likewise limit tooth and soft tissue sensitivity in lightenhanced peroxide treatments, as described herein.

In other embodiments, the peroxide density is less than about 1.2mg/cm², or less than about 1.1 mg/cm², or less than about 1 mg/cm², orless than about 0.75 mg/cm², or less than about 0.5 mg/cm², and/orgreater than about 0.01 mg/cm², or greater than about 0.1 mg/cm², orgreater than about 0.25 mg/cm², or greater than about 0.5 mg/cm² incombination with a peroxide concentration greater than about 7.5%, orgreater than about 8%, or greater than about 10%, or greater than about12%, or greater than about 16%, or greater than about 20%, and/or lessthan about 40%, or less than about 35%, or less than about 30%, or lessthan about 20%. The peroxide active can be any form that liberatesperoxide either by solubilization or hydration. All peroxide activeconcentrations expressed herein are for hydrogen peroxide andappropriate conversions must be made for other peroxide liberatingmolecules such as carbamide peroxide, calcium peroxide and sodiumpercarbonate, etc. Some other peroxide actives suitable for use with thepresent invention include calcium peroxide, carbamide peroxide, sodiumpercarbonate, benzoyl peroxide and mixtures thereof. A method fordetermining the concentration of the peroxide active is set forth in theincorporated disclosure of U.S. Pat. No. 6,949,240.

The total amount of the tooth whitening composition that is delivered tothe oral cavity will vary depending upon the size of the strip ofmaterial 12 and the concentration of the peroxide active. Generally,greater than about 0.0002 gram of tooth whitening composition isprovided with the present invention, or greater than about 0.005 gm, orgreater than about 0.01 gm, or greater than about 0.015 gm, or greaterthan about 0.02 gm, or greater than about 0.025 gm, or greater thanabout 0.05 gm, or greater than about 0.075 gm, or greater than about 0.1gm, or greater than about 0.15 gm, or greater than about 0.2 gm and/orless than about 0.3 gm, or less than about 0.2 gm, or less than about0.15 gm, or less than about 0.1 gm, or less than about 0.05 gm, or lessthan about 0.025 gm, or less than about 0.001 gm.

The tooth whitening composition loading may be greater than about 0.0005gm/cm², or greater than about 0.001 gm/cm², or greater than about 0.002gm/cm², or greater than about 0.0025 gm/cm², or greater than about 0.005gm/cm², or greater than about 0.0075 gm/cm², or greater than about 0.01gm/cm², or greater than about 0.015 gm/cm², and/or less than about 0.03gm/cm², or less than about 0.02 gm/cm², or less than about 0.015 gm/cm²,or less than about 0.01 gm/cm², or less than about 0.005 gm/cm², or lessthan about 0.001 gm/cm².

As previously discussed, the tooth whitening composition contains aperoxide active and is provided in a thin layer 12 on a strip ofmaterial 14. In order to achieve the previously described compositionloadings at the higher peroxide concentrations, the thin layer 12 oftooth whitening composition that is applied to the oral cavity may havea thickness less than about 0.3 mm, or less than about 0.2 mm, or lessthan about 0.15 mm, or less than about 0.1 mm, or less than about 0.06mm, or less than about 0.03 mm, or less than about 0.001 mm and/orgreater than about 0.0002 mm, or greater than about 0.004 mm, or greaterthan about 0.008 mm, or greater than about 0.016 mm, or greater thanabout 0.018 mm, or greater than about 0.02 mm, or greater than about 0.1mm, or greater than about 0.15 mm. These measurements are taken bymeasuring from the surface 28 (FIG. 1) of the strip of material 14 andup through the thin layer 12 of tooth whitening composition.

The peroxide dose, which is the total amount of the peroxide activewithin the thin layer of the tooth whitening composition that is appliedto the oral cavity, is less than about 100 mg, or less than about 95 mg,or less than about 85 mg, or less than about 80 mg, or less than about40 mg, or less than about 20 mg, or less than about 15 mg, or less thanabout 12 mg, or less than about 10 mg, or less than about 5 mg, or lessthan about 1 mg, and/or greater than about 0.1 mg, or greater than about0.3 mg, or greater than about 0.6 mg, or greater than about 1 mg, orgreater than about 1.5 mg, or greater than about 2 mg, or greater thanabout 10 mg.

While it is desirable for the thin layer 12 of the tooth whiteningcomposition to be a homogeneous, uniform and continuous layer, the thinlayer 12 may also be non-uniform, non-continuous, and/or heterogeneous.For example, the thin layer 12 can be a laminate or separated layers ofcomponents, an amorphous mixture of components, separate stripes orspots or other patterns of different components, or a combination ofthese structures.

The tooth whitening composition of the present invention can be providedin the form of a viscous liquid, paste, gel, solution, or any othersuitable state or phase. The tooth whitening composition can be providedin the form of a gel with a viscosity between about 200 and about1,000,000 cps at low shear rates (approximately one seconds⁻¹). Inanother embodiment, the viscosity is between about 100,000 and about800,000 cps or between about 150,000 and about 700,000 cps. In yetanother embodiment, the viscosity is between about 300,000 and about700,000 cps.

As known in the art, the tooth whitening composition also has a yieldstress. Yield stress is the amount of force on a material before thematerial begins to move. The yield stress must be high enough so thatthe tooth whitening composition is able to form a thin layer and also tohandle the disturbances caused by manufacturing, handling, and storage.The yield stress of the tooth whitening composition is between about 2Pascals and about 3000 Pascals, preferably between about 20 Pascals andabout 2000 Pascals, more preferably between about 200 Pascals and about1500 Pascals, and most preferably between about 200 Pascals and about400 Pascals.

Additional constituents of the tooth whitening composition can include,but are not limited to, water, gelling agents, humectants, pH adjustingagents, stabilizing agents, desensitizing agents, and acceleratingagents or bleach activators. In addition to the above materials, anumber of other materials can also be added to the substance. Additionalmaterials include, but are not limited to, flavoring agents, sweeteningagents such as saccharin, xylitol, opacifiers, coloring agents, andchelants such as ethylenediaminetetraacetic acid. These additionalingredients can also be used in place of the compounds disclosed above.Use of these additives and additional materials is described in greaterdetail in the incorporated disclosure of U.S. Pat. No. 6,949,240.

Example I

A randomized, parallel, split-mouth design clinical trial is conductedon thirty-five adults with a Vita Shade tooth color of A2+ who had notundergone tooth bleaching treatments in the previous two years and hadno tooth sensitivity. The subjects are randomly assigned to one of sixsequences that designate which side of the mouth and treatment theyreceive. Each subject uses a 10% hydrogen peroxide marketed whiteningstrip (CREST WHITESTRIPS PREMIUM) on their maxillary teeth for 30minutes once a day for seven days. One of the lateral incisors istreated with an LED light source (Lite-ON Technology Corporation, 720South Hillview Drive, Milpitas, Calif. 95035, part #LTL1CHTBK5 BIN: QBOY470 nm) having an intensity of about 134.7 mW/cm² (resulting from acurrent of about 50 mA supplied to the LED) and an average wavelength of468 nm for 3, 30 or 300 seconds at the end of the 30 minute strip weartime according to the randomization schedule. The other lateral incisoris treated without light enhancement to establish a control measurement.Digital images are collected at initial screening, on the fourth day ofthe treatment (“Day 4”), and the day after completion of the treatment(“Day 8”).

Treatment groups are balanced with respect to the demographics andbaseline (pre-treatment) tooth color. Each treatment (including “striponly” control treatments) results in significant (p<0.02) reduction ofb* and L* color parameters relative to baseline at each study visit. The300 second light treatment results in significantly greater yellownessreduction (Δb*), increased luminance (Δb*), and resultant color change(ΔE) relative to the corresponding control measurement, as shown inTable 2 below, with 97% greater luminance increase and 69% greateryellowness reduction at Day 8.

TABLE 2 Day 8 Tooth Whitening Efficacy with Five Minute Light RadiationTreatment Treatment Delta L* Delta a* Delta b* Delta E* Light 1.68 −0.54−1.81 2.54 No Light 0.85 −0.47 −1.07 1.72 % Difference 97% 15% 69% 48%p-value 0.047 0.46 0.002 0.031

The 30 second light treatment also results in significantly greateryellowness reduction relative to the corresponding control measurement,with 27% greater yellowness reduction at Day 8. All treatments arewell-tolerated, with no subjects discontinuing treatment because oftooth pain or oral irritation.

End-of-treatment (Day 8) results for Δb* for all three treatment timesare shown in Table 3 below:

TABLE 3 Day 8 Yellowness Reduction with Varying Light Radiation TimesAdjusted mean Change from change from Control based Treatment Baselineon adjusted means  3 sec light + strip −0.89 0.22  30 sec light + strip−1.50 −0.28 300 sec light + strip −1.66 −0.82

The relationship between exposure time and Δb* change from control basedon adjusted means is illustrated in the graph shown in FIG. 6.

Example II

A randomized, parallel, split-mouth design clinical trial is conductedon thirty-five adults with a Vita Shade tooth color of A2+ who had notundergone tooth bleaching treatments in the previous two years and hadno tooth sensitivity. The subjects are randomly assigned to one of sixsequences that designate which side of the mouth and treatment theyreceive. Each subject useds a 10% hydrogen peroxide marketed whiteningstrip (CREST WHITESTRIPS PREMIUM) on their maxillary teeth for 30minutes once a day for ten days. One of the lateral incisors is treatedwith light radiation having an average wavelength of 468 nm and anintensity of approximately 41.5 mW/cm², approximately 108 mW/cm², orapproximately 134.7 mW/cm² (corresponding to light emitted from theLTL1CHTBK5 BIN: QBOY 470 nm LED, described above, when in contact withthe whitening strip and supplied with about 10 mA, 25 mA, and 50 mA ofcurrent, respectively) for five minutes at the end of the 30 minutestrip wear time. The other lateral incisor is treated without lightenhancement to establish a control measurement. Digital images arecollected at initial screen, on the fourth day of the treatment (“Day4”), on the eighth day of the treatment (“Day 8”), and the day aftercompletion of the treatment (“Day 11”).

Treatment groups are balanced with respect to the demographics andbaseline (pre-treatment) tooth color. Each treatment (including “striponly” control treatments) results in significant (p<0.04) reduction ofyellowness (b*) as early as Day 4 and increased lightness (L*) at Day 11of the study. All light enhanced peroxide strip treatments demonstratesignificantly (p<0.0001) greater yellowness reduction (Δb*) relative totheir corresponding controls at each study visit. The ΔL* parameters arenot significantly different between the treatment groups. No significantdifferences are observed between the 41.5 mW/cm², 108 mW/cm², and 134.7mW/cm² light treatments. All treatments are well-tolerated, with onlytwo of the thirty-five total subjects reporting tooth sensitivity andtwo of the total subjects reporting oral irritation.

End-of-treatment (Day 11) results for Δb* are shown in Table 4 below:

TABLE 4 Day 11 Yellowness Reduction with Varying Light RadiationIntensity Adjusted mean Change from change from Control based TreatmentBaseline on adjusted means 10 mA light + strip −1.96 −1.07 25 mA light +strip −2.55 −1.11 50 mA light + strip −2.41 −1.19

The differences in yellowness reduction (Δb*) between the varying lightintensity enhanced treatments and the control (peroxide strip only)measurements at the end of treatment, expressed in percent improvement,are illustrated in the graph shown in FIG. 7.

The dimensions and values disclosed herein are not to be understood asbeing strictly limited to the exact numerical values recited. Instead,unless otherwise specified, each such dimension is intended to mean boththe recited value and a functionally equivalent range surrounding thatvalue. For example, a dimension disclosed as “40 mm” is intended to mean“about 40 mm.”

Every document cited herein, including any cross referenced or relatedpatent or application, is hereby incorporated herein by reference in itsentirety unless expressly excluded or otherwise limited. The citation ofany document is not an admission that it is prior art with respect toany invention disclosed or claimed herein or that it alone, or in anycombination with any other reference or references, teaches, suggests ordiscloses any such invention. Further, to the extent that any meaning ordefinition of a term in this document conflicts with any meaning ordefinition of the same term in a document incorporated by reference, themeaning or definition assigned to that term in this document shallgovern.

While particular embodiments of the present invention have beenillustrated and described, it would be obvious to those skilled in theart that various other changes and modifications can be made withoutdeparting from the spirit and scope of the invention. It is thereforeintended to cover in the appended claims all such changes andmodifications that are within the scope of this invention.

1. A method of whitening teeth, comprising: applying a whiteningcomposition to at least one tooth; maintaining the whitening compositionon the at least one tooth for a first time period; and after the firsttime period, directing a light radiation toward the at least one toothfor a second time period, the first time period having a durationgreater than 50% of a total duration of the first and second timeperiods; and removing the whitening composition from the at least onetooth.
 2. The method of claim 1, wherein the duration of the first timeperiod is at least 80% of the total duration of the time period.
 3. Themethod of claim 1, wherein the light radiation is selected forabsorption by a stain on the at least one tooth by selecting awavelength corresponding to a color substantially opposite a color ofthe stain on the 1976 CIE LAB color scale.
 4. The method of claim 1,wherein the light radiation is provided at a wavelength between about440 nm and about 490 nm.
 5. The method of claim 1, wherein nophotosensitizing agent is applied to the at least one tooth.
 6. Themethod of claim 1, wherein the total duration of the first and secondtime periods is at least 30 minutes, and the second time period is nogreater than 5 minutes.
 7. The method of claim 1, wherein the first timeperiod is sufficient to ensure dilution of peroxide concentrations ontissues surrounding the at least one tooth to less than about 2%.
 8. Themethod of claim 1, wherein the whitening composition comprises a layerthat is applied to the tooth such that the whitening composition has aperoxide density less than about 1.3 mg/cm².
 9. The method of claim 1,wherein the whitening composition comprises a peroxide active having aconcentration between about 10% and about 20% of the whiteningcomposition.
 10. The method of claim 1, wherein the whiteningcomposition is applied to the at least one tooth in a layer having athickness less than about 0.3 mm.
 11. The method of claim 1, wherein thewhitening composition is provided on a strip of material configured toblock light waves having a frequency of greater than about 700 nm. 12.The method of claim 1, further comprising maintaining the whiteningcomposition on the at least one tooth for a third time period after thesecond time period.
 13. The method of claim 1, wherein the toothwhitening composition does not include a photosensitizing agent.
 14. Themethod of claim 1, wherein removing the whitening composition from theat least one tooth comprises removing the whitening composition from theat least one tooth after the first time period and before the secondtime period.
 15. A light enhanced tooth whitening kit comprising: astrip sized to cover one or more teeth, the strip including a layer of atooth whitening composition; and a portable light source configured toemit light radiation having an intensity of no greater than about 150mW/cm².
 16. The kit of claim 15, wherein the portable light source isconfigured to emit light having a wavelength between about 440 nm andabout 490 nm.
 17. The kit of claim 15, wherein the whitening compositionis provided on a strip of material configured to block light waveshaving a frequency of greater than about 700 nm.
 18. The kit of claim15, wherein the tooth whitening composition does not include aphotosensitizing agent.
 19. The kit of claim 15, wherein the whiteningcomposition comprises a peroxide active having a concentration betweenabout 10% and about 20%.
 20. The kit of claim 15, wherein the layer oftooth whitening composition has a thickness less than about 0.3 mm. 21.The kit of claim 15, wherein the portable light source is configured toemit light radiation having an intensity of no greater than about 45mW/cm².
 22. A method of whitening teeth, comprising: applying awhitening composition including a peroxide active having a concentrationbetween about 10% and about 20% to at least one tooth in a layer havinga thickness less than about 0.3 mm and a peroxide density less thanabout 1.3 mg/cm²; maintaining the whitening composition on the at leastone tooth for a first time period of about 2 minutes to about 120minutes; and after the first time period, directing a light radiationprovided at a wavelength between about 440 nm and about 490 nm and anintensity of no greater than about 45 mW/cm² toward the at least onetooth for a second time period of about 2 minutes to about 120 minutes;and removing the whitening composition from the at least one tooth. 23.The method of claim 22, wherein removing the whitening composition fromthe at least one tooth comprises removing the whitening composition fromthe at least one tooth after the first time period and before the secondtime period.